SEARCH for Diabetes in Youth (SEARCH) is an on-going, multi-center study containing the largest and most ethnically diverse population of youth with diabetes ever studied in the US. In response to RFA-DP10-001, Component B, the SEARCH Cohort Study will utilize this unique resource by continuing the study of selected SEARCH participants to address the following Aims: 1) assess the prevalence, incidence, and risk factors for selected markers of chronic microvascular (retinopathy, nephropathy, and autonomic neuropathy) and macrovascular complications (hypertension, arterial stiffness) of diabetes;2) assess the incidence and risk factors for acute complications of diabetes including serious hypoglycemia and diabetic ketoacidosis;3) conduct surveillance of mortality;and 4) determine the degree to which barriers of care, quality of care, and transition to adult care impact diabetes-related health outcomes including quality of life. Overlaid across these Aims, we will focus on the impact of race/ethnicity and other socio-cultural factors, and biochemical dimensions of diabetes type, on diabetes-related health outcomes. The SEARCH Cohort Study will conduct an in-person research study visit on SEARCH participants incident in 2002 or later, with duration of diabetes >5 years and with baseline data completed (expected n=3699). During this study medical history, anthropometric, biochemical, physiologic, and survey data will be collected and analyzed. In collaboration with the other SEARCH clinical centers, the Ohio site will collect the data described in this proposal from all eligible cases. We expect approximately 646 Ohio subjects will be eligible to participate. For Incident 2002-2005 cases, 85% of the Ohio participants have returned for at least one follow-up visit, which is the highest study-wide response rate. The Ohio team also has the highest rate for completeness of laboratory core samples. For Incident 2006 cases, Ohio had 99% completeness, and 100% completeness for Incident 2008 cases. In this proposal the Ohio site will employ the same approach and techniques used in SEARCH 1 and 2 to maintain high subject retention rates. Thus, the Ohio site has a very high likelihood of meeting the recruitment goals in this proposal contributing significantly to the success of the SEARCH Cohort Study. This study will exploit the size and ethnic diversity of the study population to identify differences in both processes of care and health outcomes by traditional, clinical diabetes type;by the major race/ethnic groups in the US;and by employing a novel approach to segregate traditional clinical diabetes types by pathophysiologic dimensions. Thus, the SEARCH cohort study has a high likelihood of making a significant impact on the clinical care of youth with diabetes from all the major ethnic groups in the US and on national public health policy.